edsco
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| posted on 3/10/11 at 11:05 AM |
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Rose jointing wishbones: Pros and Cons
Hi all
Now that i have finished building my Spire GTR, i have taken it on a couple of track-days i am starting to notice areas of handling that could maybe
improve if there was more adjustment in the suspension and geometry etc.
At present i have poly bushes all round, but was wondering whether the step towards fully rose jointed solution is really worth it.
Its mainly on the exits of corners that i have experienced the car wanting to let go (back end) as you get back on the power. Whilst its quite
entertaining and looks good to the spectator, it aint the fastest way round the track. I want to get back on the power and be sure the car is planted.
Whilst i am a novice driver and i am sure driver tuition is something i need, i do think the mechanical grip is lacking. For road purposes i am sure
there is bags of grip but as i am not IVA ing it, it is only going to be driven on track.
Firstly, what are the pros and cons of rose jointing and secondly, are there any bods out there that are able to provide or talk me through a gradual
progression in developing the car further?
Thanks
edsco
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MikeFellows
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| posted on 3/10/11 at 11:20 AM |
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I got my Indy-R all rose jointed, so that i could do exactly what your talking about in the future
as im a complete noob, this has been a nightmare in trying to get anything remotely aligned for IVA and as few people seem to get it done, the help
available is limited
im sure it will be worth it in the end but for now its a complete pita
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alistairolsen
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| posted on 3/10/11 at 11:37 AM |
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properly rosejointed suspension wont be adjustable.
My Build Thread
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zilspeed
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| posted on 3/10/11 at 11:47 AM |
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I would suggest that the principal difference would be in the inspection and maintenance regime that you must employ when the car is all rod ends as
opposed to bushed with a degree of compliance in them.
Even a poly bush will have a measure of compliance inherent compared to a rod end. Much less than a rubber bush, but still more than a rod end.
The rod end has to accept and deal with every little load and shock it is sent.
A friend had one fail at the weekend.
Now, before I go any further, I'll state for the record that this was a rally car and I absolutely accept that there are potentially greater
shock loads in such an application.
Nevertheless, the net result of this single failed road end is a wrecked shell.
I have an image of the failed part, but not necessarily permission to share the image, so you'll forgive me for not sharing without getting
express permission first.
I'm not suggesting for a second that this should cause you to shy away from using rod ends, but equally I would suggest that you should get used
to what amounts to forensic examination of the joints on a regular basis.
I would also suggest that if you were to search out the place in the uk which is pretty well known for selling rod ends at the most competitive price,
and based on my above monologue, you may wish to choose to spend a little extra and avoid the cheapest ones.
Outwith the issued of rod ends.
What tyres are you running ?
What pressures are you running ?
Springs / dampers etc ?
You may have a lot of tweaking to do before major alterations to the car even become necessary, far less essential.
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zilspeed
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| posted on 3/10/11 at 11:48 AM |
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quote:
Originally posted by alistairolsen
properly rosejointed suspension wont be adjustable.
Why not ?
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mistergrumpy
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| posted on 3/10/11 at 12:12 PM |
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The rose joints won't have their holes running horizontally as I believe the "correct" orientation is to have them vertically
pointing to avoid the bearing popping out under high loads. The bones wouldn't be able to be moved up and down the bolt shaft to adjust them
more towards the front or back of the car and then fitted with spacers. You would still be able to unscrew the rose joint at the front a bit to try
and point the bone backwards but it's generally recommended that the whole threaded part of the joint is screwed in to prevent creating a stress
point on the shaft.
That's the official view I believe and a summary of what I read off here before deciding to do mine anyway.
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liam.mccaffrey
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| posted on 3/10/11 at 12:20 PM |
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i posted a quesroom about spherical joints and this was the result. linky
Build Blog
Build Photo Album
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alistairolsen
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| posted on 3/10/11 at 12:38 PM |
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http://www.formulastudent.de/academy/pats-corner/advice-details/article/pats-column-rod-ends-in-bending/
My Build Thread
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nick205
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| posted on 3/10/11 at 01:44 PM |
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A full rod end set-up might increase the range of adjustment and allow for finer tuning. However it won't address any inherent short comings in
the suspension geometry. The start point (IMHO) is to check the chassis and suspension pick-up points are true and and within tolerance (typically
+/- 1mm). After that check that the existing wishbones and uprights are also true and again in tolerance. Once done and corrected if necessary you
have a start point to work from and can identify where to make improvements - e.g. a full rod end set-up or re-positioned pick-up points etc.
Hopefully not teaching you to suck eggs here BTW.
Des Hammill's book on suspension set-up is a worthwhile read....
http://www.amazon.co.uk/Modify-Sportscar-Kitcar-Suspension-Spee
dpro/dp/1903706734
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TimC
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| posted on 3/10/11 at 02:08 PM |
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quote:
Originally posted by mistergrumpy
The rose joints won't have their holes running horizontally as I believe the "correct" orientation is to have them vertically
pointing to avoid the bearing popping out under high loads. The bones wouldn't be able to be moved up and down the bolt shaft to adjust them
more towards the front or back of the car and then fitted with spacers. You would still be able to unscrew the rose joint at the front a bit to try
and point the bone backwards but it's generally recommended that the whole threaded part of the joint is screwed in to prevent creating a stress
point on the shaft.
That's the official view I believe and a summary of what I read off here before deciding to do mine anyway.
All of this is true, but that doesn't necessarily rule-out using rod-ends the 'incorrect way.' As the Formula Student link points
out, using rod-ends does permit greater adjustment over fixed bearings. In addition, running them with the fixing bolt horizontal also provides a not
insignificant amount of fine-tuning. Now, assuming that you don't have a massive amount of experience with the car and what you need to do to
get a car feeling right for you - or even how your desired set-up might change over time (not least as your experience and confidence improves,) is
this flexibility not desirable over-and-above some of the benefits of a fixed, 'vertical bolt' set-up? In my view it is; by combining
relatively large and good-spec rod-ends with careful checks and maintenance I hope to make the most of what is admittedly a less than ideal
design.
Isn't that what all of us are doing with kit cars i.e. how many of us are running top-spec blueprinted engines and carbon tubs?
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mistergrumpy
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| posted on 3/10/11 at 02:16 PM |
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I totally agre Tim. This is what I considered to before I did mine. I'm just messing with the fine tuning and in fact I'm going to go out
and have a play with them now 
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alistairolsen
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| posted on 3/10/11 at 02:44 PM |
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My intention is to make some adjustable ones until I get the geometry perfect and then do a proper set with enclosed housings from those.
My Build Thread
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eddie99
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| posted on 3/10/11 at 02:50 PM |
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Cons:-
Cost - Don't last that long in comparison to polybushes
Pros:-
Less friction = more grip.
Less movement = more stable geometry
Ideally from a strength and friction point of view they would be mounted with the bolts vertically, but as it would be replacing polybushes you would
be forced to use them where the bolts were horizontal, no biggy really. Ideally you would use a smaller rose joint than the polybush bolt size will
allow so again its no real biggy but would have saved weight.
Be worth checking what spring rates and damper setting you are currently using as this kind of over steer might be cured with softer rear
springs/damping or stiffer fronts.
With a set of suspension to use as a pattern we could make all the parts required to what you want.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Talon Motorsport
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| posted on 3/10/11 at 03:32 PM |
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Putting rose joints aside, all they will do is get every thing pointing the same way. I think you need to look at why the back end steps out while on
the power.
What size tyres are you using on the back, are they too wide or too narrow, are they cheap road tyres or semi slick, what pressure are you running in
them?
What are the rear spring rates have you corner weighted the car, are the dampers set up correctly for bump and rebound?
What torque is the engine making are you asking too much of the chassis?
What diff is in the car is it a LSD or do you need one?
Before spending time and money on joints I would talk to some one who knows what they are doing with car suspension, there is alot more to it than
making it so adjustable that you don't know what to play with next.
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Neville Jones
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| posted on 3/10/11 at 03:36 PM |
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There's no reason not to use nylatron bushes for the inners, with rodends on the outers.
The inner mounts will necessarily need to be very accurately placed, to ensure free movement. Alignment takes time, but the bushes will last a
lifetime. I know of at least one big name GT car team whose development mules use this setup, and a couple of others who have used it in the past. One
even raced at a high level, found the setup better than rodends, but relented eventually and went to rodends purely because 'that's what
everyone does'. Not a good reason at all.
Whatever floats your boat..., as they say.
Cheers,
Nev.
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coyoteboy
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| posted on 3/10/11 at 04:13 PM |
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quote:
One even raced at a high level, found the setup better than rodends, but relented eventually and went to rodends purely because 'that's
what everyone does'. Not a good reason at all.
A racing team went with "what everyone does" despite thinking/having proof that something else was better - can't believe they
lasted very long? While I'm all for dispelling myths of such things, the if it was better it would surely be the one thing they chose to keep -
seeing as it's a choice they make rather than is imposed upon them (unless they're fashion whores?)
[Edited on 3/10/11 by coyoteboy]
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ashg
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| posted on 3/10/11 at 05:23 PM |
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my suggestion would be to soften the front or stiffen the rear dampers before you go to all the trouble.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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JimSpencer
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| posted on 3/10/11 at 05:35 PM |
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quote:
Originally posted by alistairolsen
http://www.formulastudent.de/academy/pats-corner/advice-details/article/pats-column-rod-ends-in-bending/
It's not often one would argue with the formula student people, but that's one of them..
'Old Formula Three or old Formula Ford' bit in particular - even the current cars use them in that manner - perfectly standard use.
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JimSpencer
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| posted on 3/10/11 at 05:45 PM |
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quote:
Originally posted by edsco
Hi all
Now that i have finished building my Spire GTR, i have taken it on a couple of track-days i am starting to notice areas of handling that could maybe
improve if there was more adjustment in the suspension and geometry etc.
At present i have poly bushes all round, but was wondering whether the step towards fully rose jointed solution is really worth it.
Its mainly on the exits of corners that i have experienced the car wanting to let go (back end) as you get back on the power. Whilst its quite
entertaining and looks good to the spectator, it aint the fastest way round the track. I want to get back on the power and be sure the car is planted.
Whilst i am a novice driver and i am sure driver tuition is something i need, i do think the mechanical grip is lacking. For road purposes i am sure
there is bags of grip but as i am not IVA ing it, it is only going to be driven on track.
Firstly, what are the pros and cons of rose jointing and secondly, are there any bods out there that are able to provide or talk me through a gradual
progression in developing the car further?
Thanks
Ok had a good look at a spire GTR the other day - should be plenty of scope for adjustment with your standard bits.
Rod ends make it easier, and give more finite control for that last little bit - but the basics of getting the car more or less in the ball park can
be done with what you've got.
Assuming it's been.
Corner weighted.
Got good shock's that are valved to suit the car.
Aligned properly
Has some rake in it.
Decent tyres
and the caster and camber are in the ball park.
Then
It sounds like you've not got enough weight transfer to the rear under acceleration, so assuming the above are done it's probably either
too stiff at the rear, droop settings are wrong or it's got the daddy of roll bar's on it..
So have a shufty at the last two, check with AB what they should be, go and get a few different springs for both ends and have a play.
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alistairolsen
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| posted on 3/10/11 at 08:04 PM |
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http://boardroom.wscc.co.uk/cgi-bin/ikonboard.cgi?act=ST&f=3&t=84209
My Build Thread
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coyoteboy
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| posted on 3/10/11 at 09:00 PM |
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quote:
even the current cars use them in that manner - perfectly standard use.
Pics?
I can't see them in this pic of the rear of a 2009
F3?
[Edited on 3/10/11 by coyoteboy]
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gallons perminute
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| posted on 4/10/11 at 08:12 AM |
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If you do not know the front of a car from the rear you are in trouble........................
Does not use rod ends, too heavy, uses spherical bearings pressed into the wishbones.
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coyoteboy
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| posted on 4/10/11 at 09:53 AM |
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<grin> - actually pasted the wrong URL into the damn box. Funny. How much of a berk do I look now!
I'm guessing there's some confusion with people about what rod ends are hence people commenting on their use when they're not used
(that I can see). A spherical bearing does not a rod end make, as you point out gpm.
[Edited on 4/10/11 by coyoteboy]
[Edited on 4/10/11 by coyoteboy]
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Neville Jones
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| posted on 4/10/11 at 11:01 AM |
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If you want to be very up to date, don't use any type of pivot on the inner end. Just bolt the carbon fibre flat moulded into the wishbone end
straight onto a flat projecting from the chassis.Two little 6mm bolts.The flex of the carbon flat is enough. For a race or two anyway, before you
change them out.
ON the FS subject; Ross Brawn when judging, gives an immediate negative or downmarking if he sees rodends in bending. It's very poor
engineering. Top and bottom outers should be sphericals in proper housings. Castor adjustment is in the inner mount. Camber should be by adjustment
shims. This all comes from Brawn's own comments.
Cheers,
Nev.
The nylatron ends will outlast a rodend by a multitude of lifes. But takes a bit more care in manufacture of the chassis and wishbone. The rodend
setup is forgiving and allows for 'tolerances' in manufacture, and is much quicker to service on the day. That's why the mules used
nylatron, the racecars rodends. Not rocket science by a long way!
[Edited on 4/10/11 by Neville Jones]
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JimSpencer
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| posted on 4/10/11 at 10:57 PM |
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Hi
Nope know what a Rod End is - and yup the Reynard that's sat in the garage has quite a few all over it, should know had to purchase quite a
few..
Oddly the picture file of the F3 cars in the Monoposto Champs sans bodywork seems to feature quite a few too..
Now not saying for one minute it's perfect and you'll notice i didn't recommend the OP to do it anyway, but like it or not them
being used like that for donkeys years makes it fairly standard practice, probably because it makes adjustment quick and reasonably accurate for a
cheap initial investement
Brawn / Current GP would indeed just throw different set of bones at 0.1mm longer/shorter of course 
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